// /*
//  * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
//  * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
//  *
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//  */
//
// package com.atguigu.src7;
// import java.io.*;
// import java.util.*;
//
// /**
//  * Hash table based implementation of the <tt>Map</tt> interface.  This
//  * implementation provides all of the optional map operations, and permits
//  * <tt>null</tt> values and the <tt>null</tt> key.  (The <tt>HashMap</tt>
//  * class is roughly equivalent to <tt>Hashtable</tt>, except that it is
//  * unsynchronized and permits nulls.)  This class makes no guarantees as to
//  * the order of the map; in particular, it does not guarantee that the order
//  * will remain constant over time.
//  *
//  * <p>This implementation provides constant-time performance for the basic
//  * operations (<tt>get</tt> and <tt>put</tt>), assuming the hash function
//  * disperses the elements properly among the buckets.  Iteration over
//  * collection views requires time proportional to the "capacity" of the
//  * <tt>HashMap</tt> instance (the number of buckets) plus its size (the number
//  * of key-value mappings).  Thus, it's very important not to set the initial
//  * capacity too high (or the load factor too low) if iteration performance is
//  * important.
//  *
//  * <p>An instance of <tt>HashMap</tt> has two parameters that affect its
//  * performance: <i>initial capacity</i> and <i>load factor</i>.  The
//  * <i>capacity</i> is the number of buckets in the hash table, and the initial
//  * capacity is simply the capacity at the time the hash table is created.  The
//  * <i>load factor</i> is a measure of how full the hash table is allowed to
//  * get before its capacity is automatically increased.  When the number of
//  * entries in the hash table exceeds the product of the load factor and the
//  * current capacity, the hash table is <i>rehashed</i> (that is, internal data
//  * structures are rebuilt) so that the hash table has approximately twice the
//  * number of buckets.
//  *
//  * <p>As a general rule, the default load factor (.75) offers a good tradeoff
//  * between time and space costs.  Higher values decrease the space overhead
//  * but increase the lookup cost (reflected in most of the operations of the
//  * <tt>HashMap</tt> class, including <tt>get</tt> and <tt>put</tt>).  The
//  * expected number of entries in the map and its load factor should be taken
//  * into account when setting its initial capacity, so as to minimize the
//  * number of rehash operations.  If the initial capacity is greater
//  * than the maximum number of entries divided by the load factor, no
//  * rehash operations will ever occur.
//  *
//  * <p>If many mappings are to be stored in a <tt>HashMap</tt> instance,
//  * creating it with a sufficiently large capacity will allow the mappings to
//  * be stored more efficiently than letting it perform automatic rehashing as
//  * needed to grow the table.
//  *
//  * <p><strong>Note that this implementation is not synchronized.</strong>
//  * If multiple threads access a hash map concurrently, and at least one of
//  * the threads modifies the map structurally, it <i>must</i> be
//  * synchronized externally.  (A structural modification is any operation
//  * that adds or deletes one or more mappings; merely changing the value
//  * associated with a key that an instance already contains is not a
//  * structural modification.)  This is typically accomplished by
//  * synchronizing on some object that naturally encapsulates the map.
//  *
//  * If no such object exists, the map should be "wrapped" using the
//  * {@link Collections#synchronizedMap Collections.synchronizedMap}
//  * method.  This is best done at creation time, to prevent accidental
//  * unsynchronized access to the map:<pre>
//  *   Map m = Collections.synchronizedMap(new HashMap(...));</pre>
//  *
//  * <p>The iterators returned by all of this class's "collection view methods"
//  * are <i>fail-fast</i>: if the map is structurally modified at any time after
//  * the iterator is created, in any way except through the iterator's own
//  * <tt>remove</tt> method, the iterator will throw a
//  * {@link ConcurrentModificationException}.  Thus, in the face of concurrent
//  * modification, the iterator fails quickly and cleanly, rather than risking
//  * arbitrary, non-deterministic behavior at an undetermined time in the
//  * future.
//  *
//  * <p>Note that the fail-fast behavior of an iterator cannot be guaranteed
//  * as it is, generally speaking, impossible to make any hard guarantees in the
//  * presence of unsynchronized concurrent modification.  Fail-fast iterators
//  * throw <tt>ConcurrentModificationException</tt> on a best-effort basis.
//  * Therefore, it would be wrong to write a program that depended on this
//  * exception for its correctness: <i>the fail-fast behavior of iterators
//  * should be used only to detect bugs.</i>
//  *
//  * <p>This class is a member of the
//  * <a href="{@docRoot}/../technotes/guides/collections/index.html">
//  * Java Collections Framework</a>.
//  *
//  * @param <K> the type of keys maintained by this map
//  * @param <V> the type of mapped values
//  *
//  * @author  Doug Lea
//  * @author  Josh Bloch
//  * @author  Arthur van Hoff
//  * @author  Neal Gafter
//  * @see     Object#hashCode()
//  * @see     Collection
//  * @see     Map
//  * @see     TreeMap
//  * @see     Hashtable
//  * @since   1.2
//  */
//
// public class HashMap<K,V>
//     extends AbstractMap<K,V>
//     implements Map<K,V>, Cloneable, Serializable
// {
//
//     /**
//      * The default initial capacity - MUST be a power of two.
//      */
//     static final int DEFAULT_INITIAL_CAPACITY = 16;
//
//     /**
//      * The maximum capacity, used if a higher value is implicitly specified
//      * by either of the constructors with arguments.
//      * MUST be a power of two <= 1<<30.
//      */
//     static final int MAXIMUM_CAPACITY = 1 << 30;
//
//     /**
//      * The load factor used when none specified in constructor.
//      */
//     static final float DEFAULT_LOAD_FACTOR = 0.75f;
//
//     /**
//      * The table, resized as necessary. Length MUST Always be a power of two.
//      */
//     transient Entry<K,V>[] table;
//
//     /**
//      * The number of key-value mappings contained in this map.
//      */
//     transient int size;
//
//     /**
//      * The next size value at which to resize (capacity * load factor).
//      * @serial
//      */
//     int threshold;
//
//     /**
//      * The load factor for the hash table.
//      *
//      * @serial
//      */
//     final float loadFactor;
//
//     /**
//      * The number of times this HashMap has been structurally modified
//      * Structural modifications are those that change the number of mappings in
//      * the HashMap or otherwise modify its internal structure (e.g.,
//      * rehash).  This field is used to make iterators on Collection-views of
//      * the HashMap fail-fast.  (See ConcurrentModificationException).
//      */
//     transient int modCount;
//
//     /**
//      * The default threshold of map capacity above which alternative hashing is
//      * used for String keys. Alternative hashing reduces the incidence of
//      * collisions due to weak hash code calculation for String keys.
//      * <p/>
//      * This value may be overridden by defining the system property
//      * {@code jdk.map.althashing.threshold}. A property value of {@code 1}
//      * forces alternative hashing to be used at all times whereas
//      * {@code -1} value ensures that alternative hashing is never used.
//      */
//     static final int ALTERNATIVE_HASHING_THRESHOLD_DEFAULT = Integer.MAX_VALUE;
//
//     /**
//      * holds values which can't be initialized until after VM is booted.
//      */
//     private static class Holder {
//
//             // Unsafe mechanics
//         /**
//          * Unsafe utilities
//          */
//         static final sun.misc.Unsafe UNSAFE;
//
//         /**
//          * Offset of "final" hashSeed field we must set in readObject() method.
//          */
//         static final long HASHSEED_OFFSET;
//
//         /**
//          * Table capacity above which to switch to use alternative hashing.
//          */
//         static final int ALTERNATIVE_HASHING_THRESHOLD;
//
//         static {
//             String altThreshold = java.security.AccessController.doPrivileged(
//                 new sun.security.action.GetPropertyAction(
//                     "jdk.map.althashing.threshold"));
//
//             int threshold;
//             try {
//                 threshold = (null != altThreshold)
//                         ? Integer.parseInt(altThreshold)
//                         : ALTERNATIVE_HASHING_THRESHOLD_DEFAULT;
//
//                 // disable alternative hashing if -1
//                 if (threshold == -1) {
//                     threshold = Integer.MAX_VALUE;
//                 }
//
//                 if (threshold < 0) {
//                     throw new IllegalArgumentException("value must be positive integer.");
//                 }
//             } catch(IllegalArgumentException failed) {
//                 throw new Error("Illegal value for 'jdk.map.althashing.threshold'", failed);
//             }
//             ALTERNATIVE_HASHING_THRESHOLD = threshold;
//
//             try {
//                 UNSAFE = sun.misc.Unsafe.getUnsafe();
//                 HASHSEED_OFFSET = UNSAFE.objectFieldOffset(
//                     HashMap.class.getDeclaredField("hashSeed"));
//             } catch (NoSuchFieldException | SecurityException e) {
//                 throw new Error("Failed to record hashSeed offset", e);
//             }
//         }
//     }
//
//     /**
//      * If {@code true} then perform alternative hashing of String keys to reduce
//      * the incidence of collisions due to weak hash code calculation.
//      */
//     transient boolean useAltHashing;
//
//     /**
//      * A randomizing value associated with this instance that is applied to
//      * hash code of keys to make hash collisions harder to find.
//      */
//     transient final int hashSeed = sun.misc.Hashing.randomHashSeed(this);
//
//     /**
//      * Constructs an empty <tt>HashMap</tt> with the specified initial
//      * capacity and load factor.
//      *
//      * @param  initialCapacity the initial capacity
//      * @param  loadFactor      the load factor
//      * @throws IllegalArgumentException if the initial capacity is negative
//      *         or the load factor is nonpositive
//      */
//     public HashMap(int initialCapacity, float loadFactor) {
//         if (initialCapacity < 0)
//             throw new IllegalArgumentException("Illegal initial capacity: " +
//                                                initialCapacity);
//         if (initialCapacity > MAXIMUM_CAPACITY)
//             initialCapacity = MAXIMUM_CAPACITY;
//         if (loadFactor <= 0 || Float.isNaN(loadFactor))
//             throw new IllegalArgumentException("Illegal load factor: " +
//                                                loadFactor);
//
//         // Find a power of 2 >= initialCapacity
//         int capacity = 1;
//         while (capacity < initialCapacity)
//             capacity <<= 1;
//
//         this.loadFactor = loadFactor;
//         threshold = (int)Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
//         table = new Entry[capacity];
//         useAltHashing = sun.misc.VM.isBooted() &&
//                 (capacity >= Holder.ALTERNATIVE_HASHING_THRESHOLD);
//         init();
//     }
//
//     /**
//      * Constructs an empty <tt>HashMap</tt> with the specified initial
//      * capacity and the default load factor (0.75).
//      *
//      * @param  initialCapacity the initial capacity.
//      * @throws IllegalArgumentException if the initial capacity is negative.
//      */
//     public HashMap(int initialCapacity) {
//         this(initialCapacity, DEFAULT_LOAD_FACTOR);
//     }
//
//     /**
//      * Constructs an empty <tt>HashMap</tt> with the default initial capacity
//      * (16) and the default load factor (0.75).
//      */
//     public HashMap() {
//         this(DEFAULT_INITIAL_CAPACITY, DEFAULT_LOAD_FACTOR);
//     }
//
//     /**
//      * Constructs a new <tt>HashMap</tt> with the same mappings as the
//      * specified <tt>Map</tt>.  The <tt>HashMap</tt> is created with
//      * default load factor (0.75) and an initial capacity sufficient to
//      * hold the mappings in the specified <tt>Map</tt>.
//      *
//      * @param   m the map whose mappings are to be placed in this map
//      * @throws  NullPointerException if the specified map is null
//      */
//     public HashMap(Map<? extends K, ? extends V> m) {
//         this(Math.max((int) (m.size() / DEFAULT_LOAD_FACTOR) + 1,
//                       DEFAULT_INITIAL_CAPACITY), DEFAULT_LOAD_FACTOR);
//         putAllForCreate(m);
//     }
//
//     // internal utilities
//
//     /**
//      * Initialization hook for subclasses. This method is called
//      * in all constructors and pseudo-constructors (clone, readObject)
//      * after HashMap has been initialized but before any entries have
//      * been inserted.  (In the absence of this method, readObject would
//      * require explicit knowledge of subclasses.)
//      */
//     void init() {
//     }
//
//     /**
//      * Retrieve object hash code and applies a supplemental hash function to the
//      * result hash, which defends against poor quality hash functions.  This is
//      * critical because HashMap uses power-of-two length hash tables, that
//      * otherwise encounter collisions for hashCodes that do not differ
//      * in lower bits. Note: Null keys always map to hash 0, thus index 0.
//      */
//     final int hash(Object k) {
//         int h = 0;
//         if (useAltHashing) {
//             if (k instanceof String) {
//                 return sun.misc.Hashing.stringHash32((String) k);
//             }
//             h = hashSeed;
//         }
//
//         h ^= k.hashCode();
//
//         // This function ensures that hashCodes that differ only by
//         // constant multiples at each bit position have a bounded
//         // number of collisions (approximately 8 at default load factor).
//         h ^= (h >>> 20) ^ (h >>> 12);
//         return h ^ (h >>> 7) ^ (h >>> 4);
//     }
//
//     /**
//      * Returns index for hash code h.
//      */
//     static int indexFor(int h, int length) {
//         return h & (length-1);
//     }
//
//     /**
//      * Returns the number of key-value mappings in this map.
//      *
//      * @return the number of key-value mappings in this map
//      */
//     public int size() {
//         return size;
//     }
//
//     /**
//      * Returns <tt>true</tt> if this map contains no key-value mappings.
//      *
//      * @return <tt>true</tt> if this map contains no key-value mappings
//      */
//     public boolean isEmpty() {
//         return size == 0;
//     }
//
//     /**
//      * Returns the value to which the specified key is mapped,
//      * or {@code null} if this map contains no mapping for the key.
//      *
//      * <p>More formally, if this map contains a mapping from a key
//      * {@code k} to a value {@code v} such that {@code (key==null ? k==null :
//      * key.equals(k))}, then this method returns {@code v}; otherwise
//      * it returns {@code null}.  (There can be at most one such mapping.)
//      *
//      * <p>A return value of {@code null} does not <i>necessarily</i>
//      * indicate that the map contains no mapping for the key; it's also
//      * possible that the map explicitly maps the key to {@code null}.
//      * The {@link #containsKey containsKey} operation may be used to
//      * distinguish these two cases.
//      *
//      * @see #put(Object, Object)
//      */
//     public V get(Object key) {
//         if (key == null)
//             return getForNullKey();
//         Entry<K,V> entry = getEntry(key);
//
//         return null == entry ? null : entry.getValue();
//     }
//
//     /**
//      * Offloaded version of get() to look up null keys.  Null keys map
//      * to index 0.  This null case is split out into separate methods
//      * for the sake of performance in the two most commonly used
//      * operations (get and put), but incorporated with conditionals in
//      * others.
//      */
//     private V getForNullKey() {
//         for (Entry<K,V> e = table[0]; e != null; e = e.next) {
//             if (e.key == null)
//                 return e.value;
//         }
//         return null;
//     }
//
//     /**
//      * Returns <tt>true</tt> if this map contains a mapping for the
//      * specified key.
//      *
//      * @param   key   The key whose presence in this map is to be tested
//      * @return <tt>true</tt> if this map contains a mapping for the specified
//      * key.
//      */
//     public boolean containsKey(Object key) {
//         return getEntry(key) != null;
//     }
//
//     /**
//      * Returns the entry associated with the specified key in the
//      * HashMap.  Returns null if the HashMap contains no mapping
//      * for the key.
//      */
//     final Entry<K,V> getEntry(Object key) {
//         int hash = (key == null) ? 0 : hash(key);
//         for (Entry<K,V> e = table[indexFor(hash, table.length)];
//              e != null;
//              e = e.next) {
//             Object k;
//             if (e.hash == hash &&
//                 ((k = e.key) == key || (key != null && key.equals(k))))
//                 return e;
//         }
//         return null;
//     }
//
//
//     /**
//      * Associates the specified value with the specified key in this map.
//      * If the map previously contained a mapping for the key, the old
//      * value is replaced.
//      *
//      * @param key key with which the specified value is to be associated
//      * @param value value to be associated with the specified key
//      * @return the previous value associated with <tt>key</tt>, or
//      *         <tt>null</tt> if there was no mapping for <tt>key</tt>.
//      *         (A <tt>null</tt> return can also indicate that the map
//      *         previously associated <tt>null</tt> with <tt>key</tt>.)
//      */
//     public V put(K key, V value) {
//         if (key == null)
//             return putForNullKey(value);
//         int hash = hash(key);
//         int i = indexFor(hash, table.length);
//         for (Entry<K,V> e = table[i]; e != null; e = e.next) {
//             Object k;
//             if (e.hash == hash && ((k = e.key) == key || key.equals(k))) {
//                 V oldValue = e.value;
//                 e.value = value;
//                 e.recordAccess(this);
//                 return oldValue;
//             }
//         }
//
//         modCount++;
//         addEntry(hash, key, value, i);
//         return null;
//     }
//
//     /**
//      * Offloaded version of put for null keys
//      */
//     private V putForNullKey(V value) {
//         for (Entry<K,V> e = table[0]; e != null; e = e.next) {
//             if (e.key == null) {
//                 V oldValue = e.value;
//                 e.value = value;
//                 e.recordAccess(this);
//                 return oldValue;
//             }
//         }
//         modCount++;
//         addEntry(0, null, value, 0);
//         return null;
//     }
//
//     /**
//      * This method is used instead of put by constructors and
//      * pseudoconstructors (clone, readObject).  It does not resize the table,
//      * check for comodification, etc.  It calls createEntry rather than
//      * addEntry.
//      */
//     private void putForCreate(K key, V value) {
//         int hash = null == key ? 0 : hash(key);
//         int i = indexFor(hash, table.length);
//
//         /**
//          * Look for preexisting entry for key.  This will never happen for
//          * clone or deserialize.  It will only happen for construction if the
//          * input Map is a sorted map whose ordering is inconsistent w/ equals.
//          */
//         for (Entry<K,V> e = table[i]; e != null; e = e.next) {
//             Object k;
//             if (e.hash == hash &&
//                 ((k = e.key) == key || (key != null && key.equals(k)))) {
//                 e.value = value;
//                 return;
//             }
//         }
//
//         createEntry(hash, key, value, i);
//     }
//
//     private void putAllForCreate(Map<? extends K, ? extends V> m) {
//         for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
//             putForCreate(e.getKey(), e.getValue());
//     }
//
//     /**
//      * Rehashes the contents of this map into a new array with a
//      * larger capacity.  This method is called automatically when the
//      * number of keys in this map reaches its threshold.
//      *
//      * If current capacity is MAXIMUM_CAPACITY, this method does not
//      * resize the map, but sets threshold to Integer.MAX_VALUE.
//      * This has the effect of preventing future calls.
//      *
//      * @param newCapacity the new capacity, MUST be a power of two;
//      *        must be greater than current capacity unless current
//      *        capacity is MAXIMUM_CAPACITY (in which case value
//      *        is irrelevant).
//      */
//     void resize(int newCapacity) {
//         Entry[] oldTable = table;
//         int oldCapacity = oldTable.length;
//         if (oldCapacity == MAXIMUM_CAPACITY) {
//             threshold = Integer.MAX_VALUE;
//             return;
//         }
//
//         Entry[] newTable = new Entry[newCapacity];
//         boolean oldAltHashing = useAltHashing;
//         useAltHashing |= sun.misc.VM.isBooted() &&
//                 (newCapacity >= Holder.ALTERNATIVE_HASHING_THRESHOLD);
//         boolean rehash = oldAltHashing ^ useAltHashing;
//         transfer(newTable, rehash);
//         table = newTable;
//         threshold = (int)Math.min(newCapacity * loadFactor, MAXIMUM_CAPACITY + 1);
//     }
//
//     /**
//      * Transfers all entries from current table to newTable.
//      */
//     void transfer(Entry[] newTable, boolean rehash) {
//         int newCapacity = newTable.length;
//         for (Entry<K,V> e : table) {
//             while(null != e) {
//                 Entry<K,V> next = e.next;
//                 if (rehash) {
//                     e.hash = null == e.key ? 0 : hash(e.key);
//                 }
//                 int i = indexFor(e.hash, newCapacity);
//                 e.next = newTable[i];
//                 newTable[i] = e;
//                 e = next;
//             }
//         }
//     }
//
//     /**
//      * Copies all of the mappings from the specified map to this map.
//      * These mappings will replace any mappings that this map had for
//      * any of the keys currently in the specified map.
//      *
//      * @param m mappings to be stored in this map
//      * @throws NullPointerException if the specified map is null
//      */
//     public void putAll(Map<? extends K, ? extends V> m) {
//         int numKeysToBeAdded = m.size();
//         if (numKeysToBeAdded == 0)
//             return;
//
//         /*
//          * Expand the map if the map if the number of mappings to be added
//          * is greater than or equal to threshold.  This is conservative; the
//          * obvious condition is (m.size() + size) >= threshold, but this
//          * condition could result in a map with twice the appropriate capacity,
//          * if the keys to be added overlap with the keys already in this map.
//          * By using the conservative calculation, we subject ourself
//          * to at most one extra resize.
//          */
//         if (numKeysToBeAdded > threshold) {
//             int targetCapacity = (int)(numKeysToBeAdded / loadFactor + 1);
//             if (targetCapacity > MAXIMUM_CAPACITY)
//                 targetCapacity = MAXIMUM_CAPACITY;
//             int newCapacity = table.length;
//             while (newCapacity < targetCapacity)
//                 newCapacity <<= 1;
//             if (newCapacity > table.length)
//                 resize(newCapacity);
//         }
//
//         for (Map.Entry<? extends K, ? extends V> e : m.entrySet())
//             put(e.getKey(), e.getValue());
//     }
//
//     /**
//      * Removes the mapping for the specified key from this map if present.
//      *
//      * @param  key key whose mapping is to be removed from the map
//      * @return the previous value associated with <tt>key</tt>, or
//      *         <tt>null</tt> if there was no mapping for <tt>key</tt>.
//      *         (A <tt>null</tt> return can also indicate that the map
//      *         previously associated <tt>null</tt> with <tt>key</tt>.)
//      */
//     public V remove(Object key) {
//         Entry<K,V> e = removeEntryForKey(key);
//         return (e == null ? null : e.value);
//     }
//
//     /**
//      * Removes and returns the entry associated with the specified key
//      * in the HashMap.  Returns null if the HashMap contains no mapping
//      * for this key.
//      */
//     final Entry<K,V> removeEntryForKey(Object key) {
//         int hash = (key == null) ? 0 : hash(key);
//         int i = indexFor(hash, table.length);
//         Entry<K,V> prev = table[i];
//         Entry<K,V> e = prev;
//
//         while (e != null) {
//             Entry<K,V> next = e.next;
//             Object k;
//             if (e.hash == hash &&
//                 ((k = e.key) == key || (key != null && key.equals(k)))) {
//                 modCount++;
//                 size--;
//                 if (prev == e)
//                     table[i] = next;
//                 else
//                     prev.next = next;
//                 e.recordRemoval(this);
//                 return e;
//             }
//             prev = e;
//             e = next;
//         }
//
//         return e;
//     }
//
//     /**
//      * Special version of remove for EntrySet using {@code Map.Entry.equals()}
//      * for matching.
//      */
//     final Entry<K,V> removeMapping(Object o) {
//         if (!(o instanceof Map.Entry))
//             return null;
//
//         Map.Entry<K,V> entry = (Map.Entry<K,V>) o;
//         Object key = entry.getKey();
//         int hash = (key == null) ? 0 : hash(key);
//         int i = indexFor(hash, table.length);
//         Entry<K,V> prev = table[i];
//         Entry<K,V> e = prev;
//
//         while (e != null) {
//             Entry<K,V> next = e.next;
//             if (e.hash == hash && e.equals(entry)) {
//                 modCount++;
//                 size--;
//                 if (prev == e)
//                     table[i] = next;
//                 else
//                     prev.next = next;
//                 e.recordRemoval(this);
//                 return e;
//             }
//             prev = e;
//             e = next;
//         }
//
//         return e;
//     }
//
//     /**
//      * Removes all of the mappings from this map.
//      * The map will be empty after this call returns.
//      */
//     public void clear() {
//         modCount++;
//         Entry[] tab = table;
//         for (int i = 0; i < tab.length; i++)
//             tab[i] = null;
//         size = 0;
//     }
//
//     /**
//      * Returns <tt>true</tt> if this map maps one or more keys to the
//      * specified value.
//      *
//      * @param value value whose presence in this map is to be tested
//      * @return <tt>true</tt> if this map maps one or more keys to the
//      *         specified value
//      */
//     public boolean containsValue(Object value) {
//         if (value == null)
//             return containsNullValue();
//
//         Entry[] tab = table;
//         for (int i = 0; i < tab.length ; i++)
//             for (Entry e = tab[i] ; e != null ; e = e.next)
//                 if (value.equals(e.value))
//                     return true;
//         return false;
//     }
//
//     /**
//      * Special-case code for containsValue with null argument
//      */
//     private boolean containsNullValue() {
//         Entry[] tab = table;
//         for (int i = 0; i < tab.length ; i++)
//             for (Entry e = tab[i] ; e != null ; e = e.next)
//                 if (e.value == null)
//                     return true;
//         return false;
//     }
//
//     /**
//      * Returns a shallow copy of this <tt>HashMap</tt> instance: the keys and
//      * values themselves are not cloned.
//      *
//      * @return a shallow copy of this map
//      */
//     public Object clone() {
//         HashMap<K,V> result = null;
//         try {
//             result = (HashMap<K,V>)super.clone();
//         } catch (CloneNotSupportedException e) {
//             // assert false;
//         }
//         result.table = new Entry[table.length];
//         result.entrySet = null;
//         result.modCount = 0;
//         result.size = 0;
//         result.init();
//         result.putAllForCreate(this);
//
//         return result;
//     }
//
//     static class Entry<K,V> implements Map.Entry<K,V> {
//         final K key;
//         V value;
//         Entry<K,V> next;
//         int hash;
//
//         /**
//          * Creates new entry.
//          */
//         Entry(int h, K k, V v, Entry<K,V> n) {
//             value = v;
//             next = n;
//             key = k;
//             hash = h;
//         }
//
//         public final K getKey() {
//             return key;
//         }
//
//         public final V getValue() {
//             return value;
//         }
//
//         public final V setValue(V newValue) {
//             V oldValue = value;
//             value = newValue;
//             return oldValue;
//         }
//
//         public final boolean equals(Object o) {
//             if (!(o instanceof Map.Entry))
//                 return false;
//             Map.Entry e = (Map.Entry)o;
//             Object k1 = getKey();
//             Object k2 = e.getKey();
//             if (k1 == k2 || (k1 != null && k1.equals(k2))) {
//                 Object v1 = getValue();
//                 Object v2 = e.getValue();
//                 if (v1 == v2 || (v1 != null && v1.equals(v2)))
//                     return true;
//             }
//             return false;
//         }
//
//         public final int hashCode() {
//             return (key==null   ? 0 : key.hashCode()) ^
//                    (value==null ? 0 : value.hashCode());
//         }
//
//         public final String toString() {
//             return getKey() + "=" + getValue();
//         }
//
//         /**
//          * This method is invoked whenever the value in an entry is
//          * overwritten by an invocation of put(k,v) for a key k that's already
//          * in the HashMap.
//          */
//         void recordAccess(HashMap<K,V> m) {
//         }
//
//         /**
//          * This method is invoked whenever the entry is
//          * removed from the table.
//          */
//         void recordRemoval(HashMap<K,V> m) {
//         }
//     }
//
//     /**
//      * Adds a new entry with the specified key, value and hash code to
//      * the specified bucket.  It is the responsibility of this
//      * method to resize the table if appropriate.
//      *
//      * Subclass overrides this to alter the behavior of put method.
//      */
//     void addEntry(int hash, K key, V value, int bucketIndex) {
//         if ((size >= threshold) && (null != table[bucketIndex])) {
//             resize(2 * table.length);
//             hash = (null != key) ? hash(key) : 0;
//             bucketIndex = indexFor(hash, table.length);
//         }
//
//         createEntry(hash, key, value, bucketIndex);
//     }
//
//     /**
//      * Like addEntry except that this version is used when creating entries
//      * as part of Map construction or "pseudo-construction" (cloning,
//      * deserialization).  This version needn't worry about resizing the table.
//      *
//      * Subclass overrides this to alter the behavior of HashMap(Map),
//      * clone, and readObject.
//      */
//     void createEntry(int hash, K key, V value, int bucketIndex) {
//         Entry<K,V> e = table[bucketIndex];
//         table[bucketIndex] = new Entry<>(hash, key, value, e);
//         size++;
//     }
//
//     private abstract class HashIterator<E> implements Iterator<E> {
//         Entry<K,V> next;        // next entry to return
//         int expectedModCount;   // For fast-fail
//         int index;              // current slot
//         Entry<K,V> current;     // current entry
//
//         HashIterator() {
//             expectedModCount = modCount;
//             if (size > 0) { // advance to first entry
//                 Entry[] t = table;
//                 while (index < t.length && (next = t[index++]) == null)
//                     ;
//             }
//         }
//
//         public final boolean hasNext() {
//             return next != null;
//         }
//
//         final Entry<K,V> nextEntry() {
//             if (modCount != expectedModCount)
//                 throw new ConcurrentModificationException();
//             Entry<K,V> e = next;
//             if (e == null)
//                 throw new NoSuchElementException();
//
//             if ((next = e.next) == null) {
//                 Entry[] t = table;
//                 while (index < t.length && (next = t[index++]) == null)
//                     ;
//             }
//             current = e;
//             return e;
//         }
//
//         public void remove() {
//             if (current == null)
//                 throw new IllegalStateException();
//             if (modCount != expectedModCount)
//                 throw new ConcurrentModificationException();
//             Object k = current.key;
//             current = null;
//             HashMap.this.removeEntryForKey(k);
//             expectedModCount = modCount;
//         }
//     }
//
//     private final class ValueIterator extends HashIterator<V> {
//         public V next() {
//             return nextEntry().value;
//         }
//     }
//
//     private final class KeyIterator extends HashIterator<K> {
//         public K next() {
//             return nextEntry().getKey();
//         }
//     }
//
//     private final class EntryIterator extends HashIterator<Map.Entry<K,V>> {
//         public Map.Entry<K,V> next() {
//             return nextEntry();
//         }
//     }
//
//     // Subclass overrides these to alter behavior of views' iterator() method
//     Iterator<K> newKeyIterator()   {
//         return new KeyIterator();
//     }
//     Iterator<V> newValueIterator()   {
//         return new ValueIterator();
//     }
//     Iterator<Map.Entry<K,V>> newEntryIterator()   {
//         return new EntryIterator();
//     }
//
//
//     // Views
//
//     private transient Set<Map.Entry<K,V>> entrySet = null;
//
//     /**
//      * Returns a {@link Set} view of the keys contained in this map.
//      * The set is backed by the map, so changes to the map are
//      * reflected in the set, and vice-versa.  If the map is modified
//      * while an iteration over the set is in progress (except through
//      * the iterator's own <tt>remove</tt> operation), the results of
//      * the iteration are undefined.  The set supports element removal,
//      * which removes the corresponding mapping from the map, via the
//      * <tt>Iterator.remove</tt>, <tt>Set.remove</tt>,
//      * <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt>
//      * operations.  It does not support the <tt>add</tt> or <tt>addAll</tt>
//      * operations.
//      */
//     public Set<K> keySet() {
//         Set<K> ks = keySet;
//         return (ks != null ? ks : (keySet = new KeySet()));
//     }
//
//     private final class KeySet extends AbstractSet<K> {
//         public Iterator<K> iterator() {
//             return newKeyIterator();
//         }
//         public int size() {
//             return size;
//         }
//         public boolean contains(Object o) {
//             return containsKey(o);
//         }
//         public boolean remove(Object o) {
//             return HashMap.this.removeEntryForKey(o) != null;
//         }
//         public void clear() {
//             HashMap.this.clear();
//         }
//     }
//
//     /**
//      * Returns a {@link Collection} view of the values contained in this map.
//      * The collection is backed by the map, so changes to the map are
//      * reflected in the collection, and vice-versa.  If the map is
//      * modified while an iteration over the collection is in progress
//      * (except through the iterator's own <tt>remove</tt> operation),
//      * the results of the iteration are undefined.  The collection
//      * supports element removal, which removes the corresponding
//      * mapping from the map, via the <tt>Iterator.remove</tt>,
//      * <tt>Collection.remove</tt>, <tt>removeAll</tt>,
//      * <tt>retainAll</tt> and <tt>clear</tt> operations.  It does not
//      * support the <tt>add</tt> or <tt>addAll</tt> operations.
//      */
//     public Collection<V> values() {
//         Collection<V> vs = values;
//         return (vs != null ? vs : (values = new Values()));
//     }
//
//     private final class Values extends AbstractCollection<V> {
//         public Iterator<V> iterator() {
//             return newValueIterator();
//         }
//         public int size() {
//             return size;
//         }
//         public boolean contains(Object o) {
//             return containsValue(o);
//         }
//         public void clear() {
//             HashMap.this.clear();
//         }
//     }
//
//     /**
//      * Returns a {@link Set} view of the mappings contained in this map.
//      * The set is backed by the map, so changes to the map are
//      * reflected in the set, and vice-versa.  If the map is modified
//      * while an iteration over the set is in progress (except through
//      * the iterator's own <tt>remove</tt> operation, or through the
//      * <tt>setValue</tt> operation on a map entry returned by the
//      * iterator) the results of the iteration are undefined.  The set
//      * supports element removal, which removes the corresponding
//      * mapping from the map, via the <tt>Iterator.remove</tt>,
//      * <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt> and
//      * <tt>clear</tt> operations.  It does not support the
//      * <tt>add</tt> or <tt>addAll</tt> operations.
//      *
//      * @return a set view of the mappings contained in this map
//      */
//     public Set<Map.Entry<K,V>> entrySet() {
//         return entrySet0();
//     }
//
//     private Set<Map.Entry<K,V>> entrySet0() {
//         Set<Map.Entry<K,V>> es = entrySet;
//         return es != null ? es : (entrySet = new EntrySet());
//     }
//
//     private final class EntrySet extends AbstractSet<Map.Entry<K,V>> {
//         public Iterator<Map.Entry<K,V>> iterator() {
//             return newEntryIterator();
//         }
//         public boolean contains(Object o) {
//             if (!(o instanceof Map.Entry))
//                 return false;
//             Map.Entry<K,V> e = (Map.Entry<K,V>) o;
//             Entry<K,V> candidate = getEntry(e.getKey());
//             return candidate != null && candidate.equals(e);
//         }
//         public boolean remove(Object o) {
//             return removeMapping(o) != null;
//         }
//         public int size() {
//             return size;
//         }
//         public void clear() {
//             HashMap.this.clear();
//         }
//     }
//
//     /**
//      * Save the state of the <tt>HashMap</tt> instance to a stream (i.e.,
//      * serialize it).
//      *
//      * @serialData The <i>capacity</i> of the HashMap (the length of the
//      *             bucket array) is emitted (int), followed by the
//      *             <i>size</i> (an int, the number of key-value
//      *             mappings), followed by the key (Object) and value (Object)
//      *             for each key-value mapping.  The key-value mappings are
//      *             emitted in no particular order.
//      */
//     private void writeObject(ObjectOutputStream s)
//         throws IOException
//     {
//         Iterator<Map.Entry<K,V>> i =
//             (size > 0) ? entrySet0().iterator() : null;
//
//         // Write out the threshold, loadfactor, and any hidden stuff
//         s.defaultWriteObject();
//
//         // Write out number of buckets
//         s.writeInt(table.length);
//
//         // Write out size (number of Mappings)
//         s.writeInt(size);
//
//         // Write out keys and values (alternating)
//         if (size > 0) {
//             for(Map.Entry<K,V> e : entrySet0()) {
//                 s.writeObject(e.getKey());
//                 s.writeObject(e.getValue());
//             }
//         }
//     }
//
//     private static final long serialVersionUID = 362498820763181265L;
//
//     /**
//      * Reconstitute the {@code HashMap} instance from a stream (i.e.,
//      * deserialize it).
//      */
//     private void readObject(ObjectInputStream s)
//          throws IOException, ClassNotFoundException
//     {
//         // Read in the threshold (ignored), loadfactor, and any hidden stuff
//         s.defaultReadObject();
//         if (loadFactor <= 0 || Float.isNaN(loadFactor))
//             throw new InvalidObjectException("Illegal load factor: " +
//                                                loadFactor);
//
//         // set hashSeed (can only happen after VM boot)
//         Holder.UNSAFE.putIntVolatile(this, Holder.HASHSEED_OFFSET,
//                 sun.misc.Hashing.randomHashSeed(this));
//
//         // Read in number of buckets and allocate the bucket array;
//         s.readInt(); // ignored
//
//         // Read number of mappings
//         int mappings = s.readInt();
//         if (mappings < 0)
//             throw new InvalidObjectException("Illegal mappings count: " +
//                                                mappings);
//
//         int initialCapacity = (int) Math.min(
//                 // capacity chosen by number of mappings
//                 // and desired load (if >= 0.25)
//                 mappings * Math.min(1 / loadFactor, 4.0f),
//                 // we have limits...
//                 HashMap.MAXIMUM_CAPACITY);
//         int capacity = 1;
//         // find smallest power of two which holds all mappings
//         while (capacity < initialCapacity) {
//             capacity <<= 1;
//         }
//
//         table = new Entry[capacity];
//         threshold = (int) Math.min(capacity * loadFactor, MAXIMUM_CAPACITY + 1);
//         useAltHashing = sun.misc.VM.isBooted() &&
//                 (capacity >= Holder.ALTERNATIVE_HASHING_THRESHOLD);
//
//         init();  // Give subclass a chance to do its thing.
//
//         // Read the keys and values, and put the mappings in the HashMap
//         for (int i=0; i<mappings; i++) {
//             K key = (K) s.readObject();
//             V value = (V) s.readObject();
//             putForCreate(key, value);
//         }
//     }
//
//     // These methods are used when serializing HashSets
//     int   capacity()     { return table.length; }
//     float loadFactor()   { return loadFactor;   }
// }
